Try the instructions given here: https://community.hughesnet.com/t5/Tech-Support/parental-controls/m-p/86196/highlight/true#M60732
The DNS referenced in the linked page (Norton ConectSafe) by maratsade has since shut down, but other companies do provide DNS services with Parental shields and/or controls. These DNS settings can also be entered into the internet adapter settings of specific devices if you want only particular devices to have the protection and not others. If it's entered as shown in the referenced post, as in into the HughesNet modem's settings, it will protect all devices that connect to the net via the HughesNet modem.
You can see some of the alternate DNS offerings mentioned in the following article...
https://geekflare.com/dns-content-filtering-software/
Yeah, I didn't check whether the DNS was still up. Thanks for adding that info.